The Corpus Callosum

This is from an interesting open-access article in Annals of
General Psychiatry
.  It describes two studies,
relating to two different catastrophic events.  The authors
examine the differences in how various risk factors may contribute to
the development of PTSD in persons of each gender.

href="http://www.annals-general-psychiatry.com/content/7/1/24/abstract">Risk
factors predict post-traumatic stress disorder differently in men and
women

Dorte M. Christiansen,Ask Elklit
Annals of General Psychiatry 2008, 7:24
doi:10.1186/1744-859X-7-24
18 November 2008

Background

About twice as many women as men develop post-traumatic
stress
disorder (PTSD), even though men as a group are exposed to more
traumatic events. Exposure to different trauma types does not
sufficiently explain why women are more vulnerable.

Methods

The present work examines the effect of age, previous
trauma,
negative affectivity (NA), anxiety, depression, persistent
dissociation, and social support on PTSD separately in men and women.
Subjects were exposed to either a series of explosions in a firework
factory near a residential area or to a high school stabbing incident.

Results

Some gender differences were found in the predictive power
of
well
known risk factors for PTSD. Anxiety predicted PTSD in men, but not in
women, whereas the opposite was found for depression. Dissociation was
a better predictor for PTSD in women than in men in the explosion
sample but not in the stabbing sample. Initially, NA predicted PTSD
better in women than in men in the explosion sample, but when compared
only to other significant risk factors, it significantly predicted PTSD
for both men and women in both studies. Previous traumatic events and
age did not significantly predict PTSD in either gender.

Conclusions

Gender differences in the predictive value of social support
on PTSD
appear to be very complex, and no clear conclusions can be made based
on the two studies included in this article.

Most diagnoses in psychiatry are not formally associated with a
particular cause.  PTSD is different, in that the definition
of
the disorder requires that a cause be identified.  

The etiological agnosticism of the diagnostic system is deliberate, and
appropriate in most cases.  After all, ascribing an etiology
to a
particular condition requires that one draw a conclusion.
 Why
draw a conclusion when you don’t have to?

But PTSD is different, because you can’t have posttraumatic stress
disorder unless it was preceded by trauma.  

The problem is, many persons are traumatized without going on to
develop PTSD.  So the trauma is not the only factor in the
etiology.  There must be either some spooky quantum-mechanical
factor, or some pre-existing predisposing factor, that makes the
difference.  Researchers have been trying to figure out what
those
risk factors are, with limited success.

Different studies have led to different conclusions.  

One reason I like the Christiansen and Elklit article is that they
explicitly refrain from drawing any conclusions.  

no clear conclusions can be made based
on the two studies included in this article

They went out and collection a bunch of observations, established some
associations, and left it at that.  They took the data as far
as
it would go.

They also do a nice job of summarizing the prior theories of “different
pathways” to the development of PTSD.  

It has been suggested that there may be more than one
pathway to PTSD [7]. Saxe et al. [8] studied child burn victims and
found that there are two separate pathways leading to PTSD: an anxiety
pathway and a dissociation pathway [8]. These two pathways are
separated by different risk factors, suggesting that different
biobehavioural systems contribute to PTSD. The anxiety pathway may be
related to the fight-or-flight system, whereas the dissociation pathway
has been connected to the animal “freeze” response.
Another
study focusing on sexually abused children also revealed the existence
of an avoidance pathway, which was more pronounced in boys than in
girls [9].

This highlights some of the difficulties that researchers encounter,
when trying to figure out which risk factors are important contributors
to the development of PTSD in an individual.  The condition we
recognized as PTSD is likely to be the culmination of a final
common
pathway, but the initial
pathways may be different for different individuals.  I tend
to
think that the final common pathway is best modeled by neurobiology,
whereas the initial pathways are best understood using psychological
models.

One annoying part of the paper deals with the possible role of
evolution:

To our knowledge, the existence of different pathways
to
PTSD has not been studied in adult samples. However, many articles
focusing on gender differences have shown that men and women have
different ways of responding to danger and expressing distress [3]. It
has been suggested that whereas males react to stress with the well
known fight-or-flight system regulated by the sympathetic nervous
system, evolutionary demands has favoured an alternative
tend-and-befriend system in women in times of threat [10]. The need of
such a system in women is assumed to have arisen because it has not
been adaptive for pregnant women or women caring for babies to run or
fight in the face of danger. Instead, evolutionary adaptive behaviour
has been tending to offspring, calming children down and getting them
out of harm’s way, and seeking protection among other members
of
the group. In support of this hypothesis it has been documented that
whereas men generally respond to traumatic events with physiological
hyperarousal and an increase in aggressive behaviours, women tend to
group together and seek social support – especially from other women
[10].

While it is fun to sit around and think about evolution and how it has
shaped behavior, I still doubt the utility of this approach.
 The
fun part of it is that you can always come to a point at which
everything fits together nicely, with the appearance of complete
explanatory power.  It makes us feel good when everything fits
together.  Sort of like finishing a jigsaw puzzle.

The Christiansen and Elklit article describes two studies that are
purely descriptive in nature.  As such, they cannot contribute
directly to our understanding of the pathophysiology of PTSD.
  This might be kind of disappointing for a
psychopharmacologist.  However, it is highly unlikely that
we’ll every find a way to treat PTSD well, with drugs alone.
 Psychotherapy and psychosocial interventions probably will be
needed for comprehensive care, regardless of what we may learn about
the biological underpinnings of the condition.  

Having a better understanding of the varied initial pathways still
could be helpful.  The way I see it, it could help inform our
psychotherapeutic interventions.  Furthermore, it could help
us figure out how best to help people in the earliest stage of
treatment, immediately after the trauma.  

Not everyone presents for treatment in the immediate aftermath of
trauma.  But for those who do, it would be very nice if we had
a way of predicting which crisis response strategies would be most
likely to be helpful.  

Though the findings in this study need to be
replicated, the potential implications for PTSD treatment are
substantial. If PTSD in men and women, at least to a certain degree,
are mediated by different risk factors then this may very well lead to
gender differences in the course and other characteristics of the
disorder. Ultimately, such gender differences may affect treatment
efficacy, so that one treatment may be effective for women but not for
men, or the other way around.

When people are in a great deal of distress, it often is helpful if
they can come to an understanding of the cause of their distress.
 At least in some cases, it is more helpful if this
understanding is personalized in some way.  A better
understanding of the differences in risk factors could be helpful in
this part of the process.